1. Field of the Invention
The present invention relates to an absorbent article, such as sanitary napkin, disposable diaper or the like, which has a surface member formed of continuous filaments.
2. Description of the Related Art
Absorbent articles, such as sanitary napkins, disposable diapers or the like are generally constructed such that a liquid impermeable backing sheet is stacked on the back side of an absorbent layer, and a liquid permeable surface member is stacked on the surface side as a liquid-receiving side.
As functions of the surface member of the absorbent article, it is required to have superior liquid permeability for permitting liquid to flow toward the absorbent layer, and to achieve high effect in preventing liquid from flowing back. Here, the phenomenon where liquid once absorbed in absorbent layer flows back toward the surface side is often referred to as xe2x80x9crewetxe2x80x9d.
For example, in Japanese Unexamined Patent Publication No. 5-176954, there is disclosed a surface member, in which a spun bonded non-woven fabric formed of hydrophobic continuous filaments and a thin paper formed of pulp fibers are stacked and the continuous filaments and the pulp fibers are entangled by action of water flow. In this prior art, by contacting the hydrophobic spun bonded non-woven fabric and the hydrophilic thin paper on the entire surface, body fluid is easily absorbed and passed by absorbing force of the pulp fibers forming the thin paper.
However, since this conventional surface member requires a process step of applying water flow, production cost becomes high. Also, since water flow is applied, basis weight becomes high and bulkiness becomes low to lack soft feeling as a surface member.
On the other hand, in Japanese Unexamined Patent Publication No. 9-510374, there is disclosed a surface member in which a first sheet and a second sheet are stacked in spaced apart relationship via a spacer to exhibit capillary effect by a gap defined between the first and second sheets to easily pass the body fluid.
However, since this conventional surface member employs complicate structure for requiring placing two sheets in spaced apart relationship by the spacer, difficulty is encountered in manufacturing and this is less practical.
On the other hand, as other prior art, there is a surface member in which a hydrophilic non-woven fabric is stacked below a hydrophobic non-woven fabric and these two kinds of non-woven fabric are adhered. In this surface member, permeability of body fluid is improved by liquid absorbing ability of the lower hydrophilic non-woven fabric.
However, in this conventional surface member, since the hydrophobic non-woven fabric and the hydrophilic non-woven fabric are adhered with a hot melt type adhesive or the like, the adhesive is inherently present on the interface between the non-woven fabrics to serve to block flow of the liquid.
On the other hand, Japanese Unexamined Utility Model Publication No. 57-13609, Japanese Unexamined Utility Model Publication No. 56-141612 and so forth, disclose absorbent articles, in which a layer of hydrophobic continuous filaments is provided on the surface side of the absorbent layer. In these absorbent articles employing the continuous filament layer as a surface layer, the surface layer has a low filament density and a high bulkiness. Therefore, it can provide soft contact feeling on the skin of a wearer. In addition, since the relatively bulky, hydrophobic filament layer is present between the absorbent layer and the skin of a wearer, flowing back of liquid once absorbed in the absorbent layer (i.e., rewet) can be easily prevented.
However, since the relatively bulky, hydrophobic filament layer is present on the surface of the absorbent layer, body fluid is difficult to penetrate into the absorbent layer to cause a defect that the body fluid may be retained in the filament layer.
The present invention has been worked out in view of the problem in the prior art set forth above. It is, therefore, an object of the present invention to provide an absorbent article having a surface member which provides soft contact feeling on the skin of a wearer, high liquid permeability and high rewet-preventing property, and which is easy to manufacture.
According to the invention, there is provided an absorbent article comprising:
a liquid permeable surface member;
a backing sheet;
an absorbent layer interposed between the surface member and the backing sheet, and
the surface member having at least two layers including an upper layer located at a liquid-receiving side surface and a lower layer located adjacent to the absorbent layer, the upper layer being formed of first continuous filaments, the lower layer being formed of second continuous filaments, the first and second continuous filaments individually extending over the entire length of the surface member, and hydrophilicity of the lower layer being higher than that of the upper layer.
For example, the first and second continuous filaments may be respectively prepared by applying a hydrophilic oil solution on surfaces of hydrophobic filaments, and durability of a hydrophilic oil solution applied to the second continuous filaments may be higher than that of a hydrophilic oil solution applied to the first continuous filaments.
In an alternative, the first and second continuous filaments may be respectively prepared by applying a hydrophilic oil solution on surfaces of hydrophobic filaments, and the application amount of the hydrophilic oil solution to the second continuous filaments may be greater than the application amount of the hydrophilic oil solution to the first continuous filaments.
In another alternative, the first continuous filaments may be hydrophobic filaments and the second continuous filaments may be hydrophilic filaments. In still another alternative, the first continuous filaments may be hydrophobic filaments not treated to be hydrophilic and the second continuous filaments may be hydrophobic filaments treated to be hydrophilic.
Preferably, a density of the first continuous filaments in the upper layer is different from a density of the second continuous filaments in the lower layer. More preferably, a density of the second continuous filaments in the lower layer is higher than a density of the first continuous filaments in the upper layer. In this case, number of crimp in the first continuous filaments and number of crimp in the second continuous filaments may be respectively in a range of 5 to 30 per 1 inch, but may be different from each other so that the difference in density is caused by the difference in number of crimp, and/or crimp modulus of elasticity of the first continuous filaments and crimp modulus of elasticity of the second continuous filaments may be respectively greater than or equal to 70%, but may be different from each other so that the difference in density is caused by the difference in crimp modulus of elasticity.
In the present invention, since the surface member is formed of the continuous filaments to have a low density and a high bulk, it provides soft contact feeling to the skin of a wearer. Especially, since the individual continuous filaments extend over the entire length of the surface member to have no fiber end appearing on the surface, the surface is made so smooth.
Moreover, since a difference in hydrophilicity is provided between the upper layer and the lower layer in the surface member of the continuous filaments, liquid permeability of the surface member is improved and the rewet-preventing effect is enhanced.
Still moreover, the surface member having the layers of different hydrophilicities can be easily manufactured by continuously feeding the continuous filaments of different hydrophilicities and by partially fixing them.